Cross-shore distribution of long-term average longshore sediment transport rate on a sandy beach exposed to waves with various directionalities

The cross-shore distribution of long-term average longshore sediment transport rate on a sandy beach exposed to waves with various directionalities was investigated. Using a process-based one-dimensional model, the cross-shore distributions of longshore sediment transport rate were simulated at 2-hour intervals for 15 years at the Hasaki coast of Japan. The simulation results showed that although the direction of average total longshore sediment transport rate was southward, the direction of predominant longshore sediment transport near the shore was northward. This was caused by the cross-shore distribution of average longshore sediment transport rate that was northward near the shore, but southward away from the shore. The cross-shore distribution was formed because when the longshore sediment transport developed only near the shore owing to relatively small waves, northward transport was dominant. However, when the transport developed both near and away from the shore owing to relatively large waves, southward sediment transport developed. These results indicate that examination of the cross-shore distribution of longshore sediment transport rate is crucial for gaining a better understanding of longshore sediment transport on a sandy beach exposed to waves with various directionalities.